1. Field of the Invention
This invention generally relates to printing machines, such as printers and typewriters, and particularly to printers and typewriters on which an ink ribbon cassette may be detachably mounted.
2. Description of the Prior Art
In a printing machine in which an ink ribbon cassette housing therein ink ribbon is detachably mounted for carrying out a printing operation using the ink ribbon supplied from the cassette, the ink ribbon becomes charged due to frictional contact with such elements as ribbon cassette, ribbon feeding belt, ribbon guide and ribbon guide roller as it travels during printing. The ink ribbon thus charged tends to hinder normal printing operation because, for example, it is attracted toward a sheet of recording paper or there occurs an electrostatic breakdown due to the charge accumulated on the cassette, which then could cause malfunctioning on the part of printer.
For this reason, in a prior art printer system using such a detachably mountable ink ribbon cassette 4, use is, for example, made of a feed roller 1 comprised of an electrically conductive material, as shown in FIG. 1. FIG. 2 schematically shows the condition in which the cassette 4 of FIG. 1 is mounted in position for printing operation. As shown, there is provided a ribbon feed motor 2 which is operatively coupled to the feed roller 1 of cassette 4 through a driving shaft 3. In this structure, the driving shaft 3 must also be comprised of an electrically conductive material thereby allowing the electrostatic charge accumulated in the cassette 4 to be discharged to the exterior.